Diagnosis. A species of the genus Trimeresurus, characterized by (1) hemipenes short and strongly spinose, similar to Trimeresurus stejnegeri; (2) an overall green dorsum, rather dark green in males with faint dark crossbands, and bright, grass-green in females; (3) size very large, with distinct sexual dimorphism: females up to at least 1100 mm SVL, males seldom if ever above 800 mm SVL; (4) a constant lack of red color in the postocular streak in both males and females; this streak is whitish yellow and rather faint in males, and often absent in females; (5) a more or less well-defined white, whitish blue, whitish yellow or even bright yellow ventrolateral stripe in both sexes, not or rarely bordered below by a thin rusty red line in some adult or subadult males, a very unusual condition in the subgroup of T. stejnegeri, and never red in subadult and adult females; (6) the constant presence of white vertebral spots in males at any age, whereas they are always absent in females; (7) tail mostly green, with only the tip or the last 20% of its length mottled with rusty brown; (8) eyes yellow or yellowish green in both sexes; (9) tail average, with a ratio TaLTL in females ranging from 0.15 to 0.165; (10) large, thick heads in both sexes, very stout in females; (11) first supralabial distinct from nasal; (12) 21 dorsal scale rows at midbody, strongly keeled; (13) an elongated snout covered with rather small scales; (14) internasals always separated by 1 or 2 (rarely 3) scales; (15) large, irregular supraoculars, as wide as internasals, separated by 11 – 15 small and smooth cephalic scales. Trimeresurus vogeli differs from all other green pitvipers by the combination of the following characters: (1) its short, spinose hemipenis; (2) its first supralabials is separated from the nasal; (3) its ventrolateral stripes nearly always white, whitish blue or whitish yellow when present, very seldom red in males; (4) white vertebral spots are always present in males, always absent in females; (5) less than 174 ventrals; (6) no more than about 25% of its tail is rusty red. These and further characters are detailed below by DAVID et al. 2001.

Pauwels, O.S.G.; David, P.; Chimsunchart, C. & Thirakhupt, K. 2003. Reptiles of Phetchaburi Province, Western Thailand: a list of species, with natural history notes, and a discussion on the biogeography at the Isthmus of Kra. Natural History Journal of Chulalongkorn University 3 (1): 23-53 - get paper here